1. Field of the Invention:
The present invention relates to a mechanical assembly which provides linear movement in response to temperature changes. More specifically, the present invention relates to improvements in thermal compensator mechanisms as employed in optical systems.
2. Description of the Prior Art:
The problem of focus distortion in optical systems due to changes in temperature has been frequently discussed in the prior art. Generally, temperature variations cause glass lenses to expand or contract and therefore vary the indices thereof. The lens mounts also tend to expand or contract due to changes in temperature and additionally affect the focal point. In order to maintain a fixed focal point throughout wide variations in temperature, many systems have been developed for compensating the above mentioned expansion and contraction.
In U.S. Pat. No. 1,325,936, compensation was achieved between two lenses by mounting each lens in separate mounting barrels and connecting the barrels at a point removed from the lenses. The two barrels were made of materials having different thermal coefficients of expansion, so that any change in temperature resulted in a separation change between the lenses corresponding to the difference between the two barrel expansions or contractions.
In U.S. Pat. No. 2,533,478, compensation was achieved by mounting the lenses in a barrel having a relatively low thermal coefficient of expansion and connecting one end of the lens barrel to an expandable sleeve having a relatively high thermal coefficient of expansion. The other end of the expandable sleeve was connected to an outer support sleeve having a relatively low thermal coefficient of expansion.
In U.S. Pat. No. 2,537,900, compensation was achieved by mounting the lenses in a barrel having a relatively low thermal coefficient of expansion and connecting one end of the lens barrel to a camera body. The camera body had a relatively high thermal coefficient of expansion to vary the position of the focal point in compensating fashion to maintain the preset focus.
My parent copending U.S. patent application Ser. No. 856,699, cited above, employs a linearly expanding and contracting compensator linkage constructed of elongated link elements having alternately dissimilar linear coefficients of expansion. The link elements are adjacently arranged in link pairs and the links in each pair are joined at a first end so to appear folded. Each link pair includes a first link element having a relatively high linear coefficient of expansion and a second link element having a relatively low linear coefficient of expansion so that the resultant movement of one end of the link pair is due to the difference between coefficients of expansion and the amount of movement of each preceding link member.
My related copending U.S. patent application Ser. No. 860,345, cited above, employs a serpentine channel having several elongated channel portions running parallel to the optic axis. The serpentine channel is formed in a relatively fixed lens barrel having a relatively high linear coefficient of expansion. A floating lens barrel is thermally compensated by a series of balls having a relatively low linear coefficient of expansion located in the serpentine channel. When the serpentine channel linearly expands with the expanding fixed lens barrel, the balls relocate along the channel due to biasing of the floating lens barrel in contact with the balls.